Steel pipe stiffening brace member and manufacturing method thereof

ABSTRACT

A method of manufacturing a steel pipe stiffening brace member which has a shaft constituted of a main shaft member and an auxiliary shaft member and a stiffening steel pipe obtained by connecting side edges of four flat steels surrounding the shaft to each other. In the stiffening steel pipe, inside nook portions facing a side edge of the main shaft member are formed in stiffening members  25  and  26  having a V- or L-shaped cross section by fillet welding, and outside corner portions  25   b  and  26   b  are formed in the stiffening members  25  and  26  by partial penetration welding. Thereafter, side edges of the stiffening members  25  and  26  are abutted against each other, outside corner portions  27   b  and  28   b  are temporarily assembled by partial penetration welding, and outside corner portions  25   b  and  26   b  and outside corner portions  27   b  and  28   b  are subjected to partial penetration welding.

TECHNICAL FIELD

The present invention relates to a steel pipe stiffening brace memberand a manufacturing method thereof, and relates particularly to a steelpipe stiffening brace member to be installed in steel structures such asbuildings and a manufacturing method thereof.

BACKGROUND ART

In a steel pipe stiffening brace member to be installed in steelstructures, a shaft member formed of flat steel is inserted into aposition of a diagonal of a stiffening steel pipe, and out-of-plane(direction at right angles to the longitudinal direction) deflection isrestrained when a compressive force acts in the longitudinal directionof the shaft member, thereby energy absorption capacity is increased.

At that time, even if the shaft member and an inner surface of thestiffening steel pipe are slid, in order to prevent generation offrictional noise and reduce friction, a liner plate is inserted into agap between them, or in order to realize reliable installation in steelstructures, a joint member (hereinafter referred to as an “end member”)with a width larger than the length of the diagonal of the stiffeningsteel pipe is installed at an end in a longitudinal direction of theshaft member.

There has been disclosed a method of manufacturing a brace member (thesame as the steel pipe stiffening brace member) which facilitatesinsertion of a liner plate and can enhance the degree of freedom in theshape of an end member (for example, see Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open No.2001-132112 (pp. 3 to 4, FIG. 2)

SUMMARY OF INVENTION Technical Problem

In the method of manufacturing a brace member disclosed in PatentLiterature 1, a pair of steel plates is subjected to bending work tohave a U-shaped or V-shaped (hereinafter also referred to as L-shaped,and the same is applied to the following description) cross section, andthe steel plates are arranged to surround the shaft member. The sideedges of the steel plates are connected to each other by welding to forma stiffening steel pipe having a rectangular cross section.

Thus, the liner plate is easily disposed, and, at the same time, theaccuracy of a gap is enhanced, thereby a stiffening effect is enhanced.Although the shape of the end member can be selected without beinginfluenced by the size of the stiffening steel pipe, there has been thefollowing problems.

(a) Since the stiffening steel pipe is long, a pressing machine with aconsiderably high performance is required in order to perform bendingwork of long flat steel with high accuracy. Thus, a fabricator islimited due to the restriction on equipment for fabrication.

(b) In a stiffening steel pipe formed by applying bending working toflat steel, the radius of curvature of an outside corner portion of thestiffening steel pipe facing the shaft member is required to be 10 timesor more the sheet thickness of flat steel when the sheet thickness offlat steel is not less than 6 mm. When the curvature radius is less than10 times the sheet thickness, special material certification is requiredto be obtained (see, Building Standard Law “First No. 3, ha,Notification No. 2464 of the Ministry of Construction, 2000”). Thus, thespecial material certification is required to be obtained in order toreliably suppress out-of-plane buckling.

Thus, as a method of manufacturing a stiffening steel pipe whicheliminates the need for bending work and can be disposed so as tosurround a shaft member, a method of welding four flat steels into arectangular shape to assemble the flat steels (hereinafter referred toas “welding tetrahedral box”) is considered. However, when the weldingtetrahedral box is used as a stiffening steel pipe having a steel pipestiffening brace member, there has been the following problems.

(c) Since the force of pressing and expanding a stiffening steel pipefrom the inside by out-of-plane buckling of the main shaft member isapplied near aside edge of the main shaft member, if partial penetrationwelding causing a non-welded portion on a sheet thickness inner surfaceside is used in the welding of the corner of the steel pipe, astiffening effect is reduced, and this becomes a starting point offracture of the steel pipe.

(d) In the welding of the corner of the steel pipe, when fullpenetration welding in which the entire sheet thickness is welded isused, backing metal needs to be provided inside the steel pipe (on thesteel pipe inner surface side), and the backing metal is in contact withthe shaft member or the liner plate, so that an appropriate clearancecannot be secured.

To solve the above problems, the present invention provides a method ofmanufacturing a steel pipe stiffening brace member, which eliminates theneed for bending work of flat steel, prevents fracture of a steel pipe,and can form a stiffening steel pipe which can secure an appropriateclearance, and a steel pipe stiffening brace member manufactured by themanufacturing method.

Solution to Problem

(1) A steel pipe stiffening brace member according to the presentinvention includes: a main shaft member formed of flat steel; and astiffening steel pipe which surrounds the main shaft member to restrainout-of-plane deformation of the main shaft member,

wherein side edges of four flat steels are butted to form an outsidecorner portion by partial penetration welding and form a steel pipeinside nook portion facing a side edge of the main shaft member byfillet welding, thereby the stiffening steel pipe is formed to have arectangular cross-sectional shape.

(2) In the steel pipe stiffening brace member according to (1), a linerplate is disposed in a gap between the inside nook portion of thestiffening steel pipe subjected to fillet welding and the side edge ofthe main shaft member.

(3) In the steel pipe stiffening brace member according to (1) or (2),an auxiliary shaft member formed of flat steel is installed on a sidesurface of the main shaft member.

(4) In the steel pipe stiffening brace member according to any of (1) to(3), an end member formed of flat steel with a width larger than alength of a diagonal of the stiffening steel pipe is installed at an endin a longitudinal direction of the main shaft member.

(5) A method of manufacturing a steel pipe stiffening brace memberaccording to the present invention having a main shaft member formed offlat steel and a stiffening steel pipe surrounding the main shaft memberto restrain out-of-plane deformation of the main shaft member, includingthe steps of:

butting side edges of a pair of flat steels to permanently weld aninside nook portion by fillet welding and intermittently temporarilyweld an outside corner portion in a longitudinal direction by partialpenetration welding, and, thus, to form a stiffening member having aV-shaped cross section;

butting side edges of a pair of the stiffening members in such a statethat the side edge of the main shaft member faces the permanently weldedinside nook portion of the stiffening member to intermittentlytemporarily weld the outside corner portion in the longitudinaldirection by partial penetration welding, and, thus, to temporarilyassemble the stiffening steel pipe having a rectangular cross section;and

permanently welding the temporarily welded outside corner portion of thestiffening steel pipe by partial penetration welding and permanentlyassembling the stiffening steel pipe.

(6) In the method of permanently assembling the stiffening steel pipeaccording to (5), among the temporarily welded outside corner potions ofthe stiffening steel pipe, two outside corner portions aresimultaneously permanently welded.

(7) The method according to (5) or (6) further includes, before the stepof temporarily assembling the stiffening steel pipe, disposing a linerplate in a gap between the permanently welded inside nook portion of thestiffening member and the side edge of the main shaft member.

(8) In the method according to any of (5) to (7), an auxiliary shaftmember formed of flat steel is installed on a side surface of the mainshaft member.

(9) In the method according to any of (5) to (8), an end member formedof flat steel with a width larger than a length of a diagonal of thestiffening steel pipe is installed at an end in a longitudinal directionof the main shaft member.

Advantageous Effects of Invention

(i) A steel pipe stiffening brace member according to the presentinvention is formed to have a rectangular cross section by butting sideedges of four flat steels to form an outside corner portion by partialpenetration welding and, at the same time, form a steel pipe inside nookportion facing a side edge of a main shaft member by fillet welding.Thus, the need for bending work of flat steel is eliminated, and, at thesame time, fracture of the stiffening steel pipe can be preventedagainst a push-out force from the inside of the steel pipe according toout-of-plane buckling of the main shaft member.

Although the inner surface nook portion except for the steel pipe insidenook portion facing the side edge of the main shaft member is notsubjected to fillet welding, a stress less than the stress applied tothe former occurs in the latter, and therefore, the stiffening steelpipe is not fractured.

Further, since backing metal is not required to be attached to the steelpipe inside nook portion facing the side edge of the main shaft member,an appropriate clearance can be secured between the stiffening steelpipe and the shaft member or the liner plate.

(ii) Since the liner plate is disposed in a gap between the inside nookportion of the stiffening steel pipe and the side edge of the main shaftmember, out-of-plane deformation (deflection) of the main shaft membercan be appropriately restrained, and, at the same time, even if both areslid, it is possible to prevent generation of frictional noise andreduce friction.

(iii) Further, since an auxiliary shaft member formed of flat steel isinstalled on a side surface of the main shaft member, out-of-planedeformation to a compression force in a longitudinal direction isrestrained, and absorption energy is increased.

(iv) Furthermore, since an end member formed of flat steel with a widthlarger than a length of a diagonal of the stiffening steel pipe isinstalled at an end in a longitudinal direction of the main shaftmember, reliable connection to steel structures is realized, and energyabsorption of the main shaft member is more reliably performed.

(v) Furthermore, a method of manufacturing a steel pipe stiffening bracemember according to the present invention includes a process of forminga stiffening member by permanently welding an inside nook by filletwelding and temporarily welding an outside corner portion by partialpenetration welding, a process of temporarily assembling a stiffeningsteel pipe by temporarily welding the outside corner portion by partialpenetration welding, and a process of permanently assembling thestiffening steel pipe by permanently welding the outside corner portionby partial penetration welding, thereby the stiffening steel pipe can beformed while eliminating the need for bending work of flat steel and, atthe same time, suppressing bentness or warpage of the steel pipe due toinfluence of welding heat.

(vi) Furthermore, since two outside corner portions of the stiffeningsteel pipe of the temporarily welded outside corner portions aresimultaneously permanently welded by semiautomatic welding machinesarranged in parallel to permanently assemble the stiffening steel pipe,the number of times of rotating the steel pipe stiffening brace memberin the welding is reduced, and the manufacturing process can beabbreviated.

(vii) The method of manufacturing a steel pipe stiffening brace memberfurther includes a process of disposing the liner plate before theprocess of temporarily assembling the stiffening steel pipe, thereby theliner plate can be easily disposed, and, at the same time, the accuracyof a gap is enhanced to enhance a stiffening effect.

(viii) Furthermore, since an auxiliary shaft member formed of flat steelis installed on a side surface of the main shaft member, out-of-planedeformation to a compression force in a longitudinal direction isrestrained, and absorption energy is increased.

(ix) Since an end member does not penetrate through the inside of thestiffening steel pipe upon manufacturing, the size and shape of the endmember are not affected by the size of the stiffening steel pipe.Accordingly, the end member formed of flat steel with a width largerthan the length of the diagonal of the stiffening steel pipe can beinstalled, reliable connection to steel structures is realized, andenergy absorption of the main shaft member is more reliably performed.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1( a) and 1(b) are, respectively, a plan view and a side viewshowing a steel pipe stiffening brace member according to the firstembodiment of the present invention.

FIGS. 2( a) and 2(b) are front cross-sectional views showing the steelpipe stiffening brace member according to the first embodiment of thepresent invention.

FIG. 3 is a flow chart for explaining a method of manufacturing a steelpipe stiffening brace member according to a second embodiment of thepresent invention.

FIGS. 4( a) to 4(c) are, respectively, a plan view, aside view, and afront cross-sectional view schematically showing each process of themethod of manufacturing a steel pipe stiffening brace member accordingto the second embodiment of the present invention.

FIGS. 5( a) to 5(d) are front cross-sectional views schematicallyshowing each process of the method of manufacturing a steel pipestiffening brace member according to the second embodiment of thepresent invention.

FIGS. 6( a) and 6(b) are front cross-sectional views schematicallyshowing a sixth process (S6) of a method of manufacturing a steel pipestiffening brace member according to a third embodiment of the presentinvention.

FIGS. 7( a) to 7(d) are, respectively, a plan view, aside view, andfront cross-sectional views of a test body used in a performancecomparison experiment in an example.

FIGS. 8( a) to 8(c) are front cross-sectional views schematicallyshowing variations of a stiffening steel pipe in the method ofmanufacturing a steel pipe stiffening brace member according to thesecond embodiment.

FIGS. 9( a) to 9(c) are partially transmitted side views schematicallyshowing variations of a steel pipe stiffening brace member in the methodof manufacturing a steel pipe stiffening brace member according to thesecond embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIGS. 1 and 2 are views for explaining a steel pipe stiffening bracemember according to a first embodiment of the present invention. FIG. 1(a) is a plan view, and FIG. 1( b) is a side view. FIG. 2( a) is a frontcross-sectional view (X-X cross section in FIG. 1( b)), and FIG. 2( b)is a partially enlarged front cross-sectional view of FIG. 2( a). Thoseviews are schematic views, and the relative size of each member, sheetthickness, and the like are not limited to illustrated dimension. In thedescription of common members, suffixes “a” and “b” of referencenumerals are omitted.

(Steel Pipe Stiffening Brace Member)

In FIGS. 1 and 2, a steel pipe stiffening brace member 100 has a shaftmember 10, a stiffening steel pipe 20 surrounding the shaft member 10for restraining out-of-plane deformation of a main shaft member, endmembers (corresponding to joint members) 30 a and 30 b fixed to bothends in the longitudinal direction of the shaft member 10 respectivelyfor realizing reliable installation to steel structures (not shown), andliner plates 40 a and 40 b arranged in a gap between a side edge of theshaft member 10 and an inner surface of the stiffening steel pipe 20.

(Shaft Member)

The shaft member 10 is constituted of a main shaft member 11 formed of aflat steel shorter than the stiffening steel pipe 20 and auxiliary shaftmembers 12 and 13 formed of flat steels fixed to both side surfaces ofthe main shaft member 11 and has a cross-shaped cross section. At thistime, a distance (hereinafter referred to as “width B2”) between a sideedge of the auxiliary shaft member 12 and a side edge of the otherauxiliary shaft member 13 is smaller than a distance (hereinafterreferred to as “width B1”) between both side edges of the main shaftmember 11 (B2<B1).

The present invention is not limited to the embodiment illustrating theshaft member 10, and only the main shaft member 11 may be providedwithout fixing the auxiliary shaft members 12 and 13.

(Stiffening Steel Pipe)

The stiffening steel pipe 20 has a tubular shape with a square crosssection longer than the shaft member 10, and side edges of four flatsteels 21, 22, 23, and 24 are connected to each other by welding.

Namely, a side end surface of the flat steel 22 is abutted against aside surface of the flat steel 21 to provide a V-shaped cross section,and an inside nook portion (abutting portion on a concave surface side)25 a is connected by fillet welding W1, and an outside corner portion(abutting portion on a convex surface side) 25 b is connected by partialpenetration welding W4 (intermittent partial penetration welding W24 inthe longitudinal direction).

The fillet welding W1 and the partial penetration welding W4 (theintermittent partial penetration welding W24 in the longitudinaldirection) are similarly performed at an inside nook portion 26 a and anoutside corner portion 26 b at which the flat steels 23 and 24 areabutted against each other.

Further, the side end surface of the flat steel 24 is abutted againstthe side surface of the flat steel 21 to provide a V-shaped crosssection, and a corner portion (abutting portion on the convex surfaceside) 28 b is connected by partial penetration welding W5 (intermittentpartial penetration welding W35 in the longitudinal direction). At thistime, a corner portion (abutting portion on the concave surface side) isnot subjected to fillet welding. Note that since connection between theflat steel 23 and the flat steel 22 is similar to above, the descriptionwill be omitted.

The stiffening steel pipe 20 is formed by the above welding method andthus is less likely to cause bentness and warpage, and therefore, thestiffening steel pipe 20 is not required to be straightened (this willbe described in detail in a second embodiment).

(End Member)

The end members 30 a and 30 b (hereinafter correctively or individuallyreferred to as “end member 30”) have a main end member 31 fixed to anend in the longitudinal direction of the main shaft member 11 andauxiliary end members 32 and 33 fixed to an end in the longitudinaldirection of the auxiliary shaft members 12 and 13. The auxiliary endmembers 32 and 33 are fixed to both side surfaces of the main end member31 to provide a cross-shaped cross section.

At that time, the width of the main end member 31 and the auxiliary endmember 32 is small within a range close to the stiffening steel pipe 20in a longitudinal direction, and the main end member 31 and theauxiliary end member 32 enter inside the stiffening steel pipe 20.Meanwhile, near the end in the longitudinal direction projecting fromthe stiffening steel pipe 20, a distance between both side edges of themain end member 31 (hereinafter referred to as “width B3”) and adistance between the side edge of the auxiliary end member 32 and theside edge of the other auxiliary end members 33 (hereinafter referred toas “width B4”) are satisfactorily larger than the length of the diagonalof the inner surface of the stiffening steel pipe 20.

In the above description, although the main end member 31 and theauxiliary end members 32 and 33 have through-holes 34 and the likethrough which a bolt for installation to steel structures penetrates,the present invention is not limited to the illustrated embodiment. Forexample, the ends of the main end member 31 and the ends of theauxiliary end members 32 and 33 may be connected to a steel structure bywelding without providing the through-hole 34 and the like. In thiscase, a gazette plate whose end is formed into the same shape as an endformed by the main end member 31 and the auxiliary end members 32 and 33is installed in the steel structure.

(Liner Plate)

The liner plate 40 is disposed in a gap between the side edge of themain shaft member 11 and the inner surface of the stiffening steel pipe20. In the out-of-plane deformation (deflection) of the main shaftmember 11, a deformation volume restraining out-of-plane deformation isproperly set, and the stiffening effect is enhanced. The side edge ofthe main shaft member 11 and the inner surface of the stiffening steelpipe 20 are abutted against each other through the liner plate 40 and dono directly slid, and thereby it contributes to prevention of generationof frictional noise and reduction of friction.

A material forming the liner plate is not limited to a specific one, andhard synthetic resin may be used, or natural rubber, artificial rubber,or the like may be used.

Second Embodiment

FIGS. 3 to 5 are views for explaining a method of manufacturing a steelpipe stiffening brace member according to a second embodiment of thepresent invention. FIG. 3 is a flow chart showing each process. FIG. 4(a) is a plan view schematically showing each process. FIG. 4( b) is aside view of FIG. 4( a). FIG. 4( c) is a front cross-sectional view ofFIG. 4( a) (X-X cross section in FIG. 4 (b)). FIGS. 5( a) to 5(d) arefront cross-sectional views schematically showing each process. The sameor corresponding components as those of the first embodiment areassigned the same reference numerals, and description thereof ispartially omitted.

In FIGS. 3 and 4, the method of manufacturing a steel pipe stiffeningbrace member includes a first process (S1) of fixing the auxiliary shaftmembers 12 and 13 formed of flat steel to both side surfaces of the mainshaft member 11 formed of flat steel and forming the shaft member 10having a cross-shaped cross section and a second process (S2) of fixingthe end members 30 a and 30 b having a cross-shaped cross section toboth ends of the shaft member 10.

At that time, the auxiliary end members 32 and 33 are fixed to both sidesurfaces of the main end member 31 to form the end member 30 having across-shaped cross section; thereafter, the main end member 31 may befixed to the main shaft member 11, and the auxiliary end members 32 and33 may be fixed respectively to the auxiliary shaft members 12 and 13.Alternatively, the main end member 31 is fixed to the main shaft member11, and the auxiliary end members 32 and 33 are fixed respectively tothe auxiliary shaft members 12 and 13, and then the end member 30 havinga cross-shaped cross section may be formed.

Alternatively, the main end member 31 and the main shaft member 11 areconnected to each other, and the auxiliary end members 32 and 33 and theauxiliary shaft members 12 and 13 may be fixed to the main end member 31and the main shaft member 11 in the connected state, namely, the firstand second processes may be simultaneously executed.

In FIGS. 3 and 5( a), stiffening members 25 and 26 are then formed.Namely, the method of manufacturing a steel pipe stiffening brace memberincludes a third process (S3) of abutting an end surface of the flatsteel 22 against the side surface of the flat steel 21 to form aV-shaped cross section, and, thus, to permanently weld the inside nookportion 25 a by the fillet welding W1, and, at the same time,intermittently temporarily weld a corner portion 25 b on a convexsurface side (hereinafter referred to as an “outside corner portion”) inthe longitudinal direction by partial penetration welding W2, therebythe stiffening member 25 having a V-shaped cross section is formed, andthe stiffening member 26 is formed in a similar manner. Hereinafter, theabutting portion may be referred to as “main shaft member nook portion”.

At that time, since a chamfering (C chamfering) process is previouslyapplied to both side edges of the flat steel 22, an outer surface cornerportion has a single bevel groove (single edge beveling) whose bottom islocated at an intermediate portion of the sheet thickness of the flatsteel 22. With regard to the flat steels 23 and 24, the stiffeningmember 26 is formed in a similar manner.

In the partial penetration welding W2, a penetration depth is smallerthan the sheet thickness of the flat steel 22, and non-welded portionsremain. There is intermittent welding penetration in the longitudinaldirection (the axial direction of the stiffening steel pipe 20). Thepartial penetration welding W2 means paddings of single or few layerswith a length of 50 mm provided at an interval of 1 m.

The method of manufacturing a steel pipe stiffening brace member furtherincludes a fourth process (S4) in FIGS. 3 and 5( b) of abutting theliner plates 40 a and 40 b against both side edges of the main shaftmember 11 of the shaft member 10.

In FIGS. 3 and 5C, the stiffening steel pipe 20 surrounding the shaftmember 10 is then temporarily assembled. Namely, the manufacturingmethod furthermore includes a fifth process (S5) of surrounding theshaft member 10 with the stiffening members 25 and 26 so that both sideedges of the main shaft member 11 of the shaft member 10 face the insidenook portions of the stiffening members 25 and 26 through the linerplates 40 and, at the same time, abutting the side edges of thestiffening members 25 and 26 (to be precise, the side edges of the flatsteels 22 and 23 and the side edges of the flat steels 24 and 21)against each other to intermittently temporarily weld the outside cornerportions 27 b and 28 b in the longitudinal direction by partialpenetration welding W3, and, thus, to temporarily assemble thestiffening steel pipe 20 having a rectangular cross section.

At that time, inside nook portions 27 a and 28 a formed at the abuttingportion (hereinafter also referred to as “auxiliary shaft member nookportion”) between the side edges of the stiffening members 25 and 26 arenot subjected to welding. In accordance with the partial penetrationwelding W2, in the partial penetration welding W3, the penetration depthis smaller than the sheet thickness of the flat steels 22 and 24, andnon-welded portions remain in the sheet thickness direction. Since thepartial penetration welding W3 is intermittently performed in thelongitudinal direction, a welded portion formed by welding from outsideis not melted in the inside nook portions 27 a and 28 a.

In FIGS. 3 and 5( d), the stiffening steel pipe 20 is then permanentlyassembled. Namely, the method of manufacturing a steel pipe stiffeningbrace member furthermore includes a sixth process (S6) of permanentlywelding the outside corner portions 25 b, 26 b, 27 b, and 28 b,subjected to the partial penetration welding W2 and W3, by the partialpenetration welding W4 and W5 and permanently assembling the stiffeningsteel pipe 20.

At that time, the outside corner portions 25 b and 26 b areintermittently subjected to the partial penetration welding W2 in thelongitudinal direction, so that partial penetration welding W24 in whichthe partial penetration welding W4 is melted on the partial penetrationwelding W2 is partially executed.

Similarly, the outside corner portions 27 b and 28 b are intermittentlysubjected to the partial penetration welding W3 in the longitudinaldirection, so that partial penetration welding W35 in which the partialpenetration welding W5 is melted on the partial penetration welding W3is partially executed.

As described above, in the method of manufacturing a steel pipestiffening brace member according to the present invention, the shaftmember 10 fixed with the end member 30 is surrounded by a pair of thestiffening members 25 and 26 whose outside corner portions 25 b and 26 bare temporarily welded. The outside corner portions 27 b and 28 b of thepair of the stiffening members 25 and 26 are temporarily welded totemporarily assemble the stiffening steel pipe 20. The stiffening steelpipe 20 is then permanently welded to be permanently assembled in astate of holding the rectangular shape. Therefore, it is possible toeliminate the need for the bending work of the flat steel 21 and thelike and form the stiffening steel pipe 20 in which bentness or warpageof the flat steel 21 and the like due to the influence of welding heatin the permanently welding is suppressed.

Third Embodiment

FIGS. 6( a) and 6(b) are views for explaining a method of manufacturinga steel pipe stiffening brace member according to a third embodiment ofthe present invention and are front cross-sectional views schematicallyshowing the sixth process (S6). The same or corresponding components asthose of the second embodiment are assigned the same reference numerals,and description thereof is partially omitted.

In the third embodiment, the sixth process (S6) in the second embodimentis executed by a welding machine (semiautomatic welding machine)provided with two series of welding torches. A welding machine 70 has aworking table 71, a working stand 72, a working arm 73 movably installedon the working stand 72, welding torches 60 a and 60 b installed in theworking arm 73, power supply means (including control means) (not shown)which supplies a predetermined current to the welding torches 60 a and60 b, and material supply means (not shown) which supplies a weldingmaterial (such as welding wire and inert gas) to the welding torches 60a and 60 b.

In FIG. 6( a), the stiffening steel pipe 20 is placed on the workingtable 71 by being rotated so that the flat steel 24 (see, FIG. 5( d))having the single bevel grooves on both sides is horizontal and on thetopside.

Then, in the installation, torch tip ends 61 a and 61 b are locateddirectly above the single bevel grooves (outside corner portions) 26 band 28 b formed on both sides of the flat steel 24.

Thus, the working arm 73 is then moved (the torch tip ends 61 a and 61 brun parallel to the longitudinal direction of the stiffening steel pipe20) to apply partial penetration welding to the outside corner portions26 b and 28 b at once.

Next, the stiffening steel pipe 20 is reversed by 180 degrees andinstalled so that the flat steel 22 is horizontal and on the topside.Hereinafter, partial penetration welding is applied to the outsidecorner portions 25 b and 27 b at once by a similar procedure.

As described above, among the temporarily welded outside cornerportions, the two outside corner portions are simultaneously permanentlywelded to permanently assemble the stiffening steel pipe 20, andtherefore, bentness or warpage of the steel pipe due to influence ofwelding heat can be suppressed.

Note that either of the flat steel 24 and the flat steel 22 may bewelded first.

The present invention does not limit the configuration of the weldingmachine 70, and the working table 71 may be moved instead of the workingarm 73. The welding torches 60 a and 60 b may be installed on differentworking arms.

In FIG. 6( b), the single bevel grooves are formed on one side of theflat steel 21, one side of the flat steel 23, and both sides of the flatsteel 24. Although the flat steel 22 has no single bevel groove, theoutside corner portions 25 b, 26 b, 27 b, and 28 b are formed at therespective corners in accordance with FIG. 6( a).

The stiffening steel pipe 20 is placed on the working table 71 by beingrotated so that the outside corner portions 27 b and 28 b are horizontaland on the topside.

Thus, in the installation, the torch tip ends 61 a and 61 b are locateddirectly above the outside corner portions 27 b and 28 b, and theworking arm 73 is moved (the torch tip ends 61 a and 61 b run parallelto the longitudinal direction of the stiffening steel pipe 20) to applypartial penetration welding to the outside corner portions 27 b and 28 bat once.

Next, the stiffening steel pipe 20 is reversed by 180 degrees andinstalled so that the outside corner portions 25 b and 26 b arehorizontal and on the topside. Hereinafter, partial penetration weldingis applied to the outside corner portions 25 b and 26 b at once by asimilar procedure.

Accordingly, similar effects obtained by the welding method shown inFIG. 6 a can be obtained.

EXAMPLE

Next, there will be described experiments for comparing the performancebetween an example of the steel pipe stiffening brace member accordingto the first embodiment (the same as the steel pipe stiffening bracemember manufactured by the method of manufacturing a steel pipestiffening brace member according to the second embodiment andhereinafter also referred to as “welding tetrahedral box type”) and acomparative example that is a steel pipe stiffening brace member(hereinafter also referred to as “V-shaped pressing type”) obtained byapplying bending work to a pair of steel plates to form the crosssections of the pair of steel plates into a V-shape, and, thus, toarrange the pair of steel plates so that the pair of steel platessurrounds a shaft member and welding their end edges to each other toform a stiffening steel pipe having a rectangular cross section.

FIGS. 7( a) to 7(d) is a view for explaining a test body used in theexperiment. FIG. 7( a) is a plan view of the example. FIG. 7( b) is aside view of the example. FIG. 7C is a front cross-sectional view of theexample (A-A cross section in FIG. 7( a)). FIG. 7( d) is a frontcross-sectional view of the comparative example.

In the example in FIGS. 7( a) to 7(c), when the sheet thickness of asteel pipe is 9 mm, in the inside fillet welding, the leg length is 3mm. In outside partial penetration welding, the groove angle is 45degrees, and the groove depth is 7 mm.

In FIG. 7( d), in the comparative example, although the shape of thecross section of the shaft member, the steel pipe diameter, and thesheet thickness are the same as those in the example, a method ofmanufacturing a stiffening steel pipe is different from that in theexample.

Table 1 shows specifications of the example and the comparative exampleand the results of a constant amplitude loading test.

“Repeat count” in Table 1 is an index showing fatigue characteristics asa steel pipe stiffening brace member and shows the number of times ofrepetition until the bearing force is reduced from the maximum bearingforce of the shaft member to 70% of the maximum bearing force.“Cumulative plastic deformation ratio” in Table 1 is an index showingthe energy absorption capacity as a steel pipe stiffening brace memberand shows a value obtained by dividing an inside area of a hysteresiscurve (bearing force−deformation curve) obtained until reaching therepeat count by a rectangular area of “yield resistance×yielddeformation”.

TABLE 1 Experimental result Cumulative Shaft member Stiffening steelplate plastic Steel Cross-sectional Steel Cross-sectional FabricationRepeat deformation Test body grade shape grade shape method count ratioExample LY225 152^(B) × 94^(H) × 16^(t) SS400 140^(D) × 9^(t) Welding 482064 tetrahedral box type Comparative LY225 152^(B) × 94^(H) × 16^(t)SS400 140^(D) × 9^(t) V-shaped 45 2240 Example pressing type

In Table 1, the repeat count in the example (welding tetrahedral boxtype) is slightly greater than that in the comparative example (V-shapedpressing type).

Meanwhile, although the cumulative plastic deformation ratio in theexample is slightly lower than that in the comparative example, bothcumulative plastic deformation ratios are satisfactorily large values incomparison with “300” that is a necessary cumulative plastic deformationratio corresponding to two large earthquakes. Since it can be said thata difference between them falls within a range of variation, the exampleis equivalent to the comparative example, and it can be said that theexample has a satisfactory performance.

In the example, a rapid lowering of the bearing force does not occureven after the bearing force is less than 70% of the maximum bearingforce, and fracture at a steel pipe welding portion does not occurfinally.

(Variation)

FIGS. 8( a) to 9(c) are views schematically showing variations of thestiffening steel pipe in the method of manufacturing a steel pipestiffening brace member according to the second embodiment. FIGS. 8( a)to 8(c) are front cross-sectional views. FIGS. 9( a) and 9(b) are frontcross-sectional views showing a manufacturing process, and FIG. 9C is apartially transmitted side view of a finished product. The same orcorresponding components as those of the first embodiment are assignedthe same reference numerals, and description thereof is partiallyomitted.

In FIG. 8( a), chamfering (C chamfering) process is applied to both sideedges of the flat steels 22 and 24, and the flat steels 21 and 23 remainhave a rectangular cross-sectional shape (see, FIG. 2). FIG. 6( a) whichis a view for explaining the third embodiment shows an examplecorresponding to the stiffening steel pipe 20 of FIG. 8( a).

In FIG. 8( b), chamfering (C chamfering) process is applied to one sideedges of all the flat steels 21, 22, 23, and 24.

In FIG. 8( c), chamfering (C chamfering) process is applied to one sideedges of the flat steels 21 and 23 and both side edges of the flat steel24, and the flat steel 22 remains have a rectangular cross-sectionalshape. FIG. 6( b), which is a view for explaining the third embodiment,shows an example corresponding to the stiffening steel pipe 20 of FIG.8C.

In FIG. 9( a), positioning members 50 a and 50 b are installed withpredetermined intervals at three portions in the longitudinal directionof the side edges of the stiffening members 25 and 26 having a V-shapedcross section.

In the fifth process shown in FIGS. 9( b) and 9(c), the stiffening steelpipe 20 is temporarily assembled. At this time, the stiffening steelpipe 20 with high shape accuracy is temporarily assembled because thepositioning members 50 a and 50 b facilitate positioning between thestiffening members 25 and 26 and enhance the matching accuracy of both.

Since the positioning members 50 a and 50 b are not strength members ofthe stiffening steel pipe 20, they are installed to such an extent thatthey serves to positioning (such as spot welding). The number of thepositioning members 50 a and 50 b is not limited, and the positioningmembers 50 a and 50 b may be installed respectively to the flat steels22 and 24 instead of the flat steels 21 and 23. Further, the positioningmembers 50 a and 50 b may be installed after the formation of thestiffening members 25 and 26 (after the execution of the fillet weldingW1 and the partial penetration welding W2), and the stiffening members25 and 26 may be formed using the flat steels 21 and 23 previouslyinstalled with the positioning members 50 a and 50 b.

INDUSTRIAL APPLICABILITY

According to the present invention, the need for bending work of flatsteel is eliminated, and a stiffening steel pipe which suppressesbentness and warpage due to the influence of welding heat can be formed;therefore, the present invention can be widely used as a method ofmanufacturing brace members in various forms and a brace membermanufactured by the manufacturing method.

REFERENCE SIGNS LIST

-   10 Shaft member-   11 Main shaft member-   12 Auxiliary shaft member-   13 Auxiliary shaft member-   20 Stiffening steel pipe-   21 Flat steel-   22 Flat steel-   23 Flat steel-   24 Flat steel-   25 Stiffening member-   25 a Inside corner portion-   25 b Outside corner portion-   26 Stiffening member-   26 a Inside corner portion-   26 b Outside corner portion-   27 a Inside nook portion-   27 b Outside corner portion-   28 a Inside nook portion-   28 b Outside corner portion-   30 End member-   31 Main end member-   32 Auxiliary end member-   33 Auxiliary end member-   34 Through-hole-   35 Through-hole-   40 Liner plate-   50 Positioning member-   70 Welding machine-   100 Steel pipe stiffening brace member-   B1 Width (main shaft member)-   B2 Width (auxiliary shaft member)-   B3 Width (main end member)-   B4 Width (auxiliary end member)-   W1 Fillet welding-   W2 Partial penetration welding-   W3 Partial penetration welding-   W4 Partial penetration welding-   W5 Partial penetration welding-   W24 Partial penetration welding-   W35 Partial penetration welding

1. A steel pipe stiffening brace member comprising: a main shaft memberformed of flat steel; and a stiffening steel pipe which surrounds themain shaft member to restrain out-of-plane deformation of the main shaftmember, wherein side edges of four flat steels are butted to form anoutside corner portion by partial penetration welding and form a steelpipe inside nook portion facing a side edge of the main shaft member byfillet welding, thereby the stiffening steel pipe is formed to have arectangular cross-sectional shape.
 2. The steel pipe stiffening bracemember according to claim 1, wherein a liner plate is disposed in a gapbetween the inside nook portion of the stiffening steel pipe subjectedto fillet welding and the side edge of the main shaft member.
 3. Thesteel pipe stiffening brace member according to claim 1, wherein anauxiliary shaft member formed of flat steel is installed on a sidesurface of the main shaft member.
 4. The steel pipe stiffening bracemember according to claim 1, wherein an end member formed of flat steelwith a width larger than a length of a diagonal of the stiffening steelpipe is installed at an end in a longitudinal direction of the mainshaft member.
 5. A method of manufacturing a steel pipe stiffening bracemember, which comprises a main shaft member formed of flat steel and astiffening steel pipe surrounding the main shaft member to restrainout-of-plane deformation of the main shaft member, comprising the stepsof: butting side edges of a pair of flat steels to permanently weld aninside nook portion by fillet welding and intermittently temporarilyweld an outside corner portion in a longitudinal direction by partialpenetration welding, and, thus, to form a stiffening member having aV-shaped cross section; butting side edges of a pair of the stiffeningmembers in such a state that the side edge of the main shaft memberfaces the permanently welded inside nook portion of the stiffeningmember to intermittently temporarily weld the outside corner portion inthe longitudinal direction by partial penetration welding, and, thus, totemporarily assemble the stiffening steel pipe having a rectangularcross section; and permanently welding the temporarily welded outsidecorner portion of the stiffening steel pipe by partial penetrationwelding and permanently assembling the stiffening steel pipe.
 6. Themethod of manufacturing a steel pipe stiffening brace member accordingto claim 5, wherein in the step of permanently assembling the stiffeningsteel pipe, among the temporarily welded outside corner potions of thestiffening steel pipe, two outside corner portions are simultaneouslypermanently welded.
 7. The method of manufacturing a steel pipestiffening brace member according to claim 5, further comprising, beforethe step of temporarily assembling the stiffening steel pipe, disposinga liner plate in a gap between the permanently welded inside nookportion of the stiffening member and the side edge of the main shaftmember.
 8. The method of manufacturing a steel pipe stiffening bracemember according to claim 5, wherein an auxiliary shaft member formed offlat steel is installed on a side surface of the main shaft member. 9.The method of manufacturing a steel pipe stiffening brace memberaccording to claim 5, wherein an end member formed of flat steel with awidth larger than a length of a diagonal of the stiffening steel pipe isinstalled at an end in a longitudinal direction of the main shaftmember.
 10. The method of manufacturing a steel pipe stiffening bracemember according to claim 6, further comprising, before the step oftemporarily assembling the stiffening steel pipe, disposing a linerplate in a gap between the permanently welded inside nook portion of thestiffening member and the side edge of the main shaft member.
 11. Themethod of manufacturing a steel pipe stiffening brace member accordingto claims 6, wherein an auxiliary shaft member formed of flat steel isinstalled on a side surface of the main shaft member.
 12. The method ofmanufacturing a steel pipe stiffening brace member according to claims7, wherein an auxiliary shaft member formed of flat steel is installedon a side surface of the main shaft member.
 13. The method ofmanufacturing a steel pipe stiffening brace member according to claim 6,wherein an end member formed of flat steel with a width larger than alength of a diagonal of the stiffening steel pipe is installed at an endin a longitudinal direction of the main shaft member.
 14. The method ofmanufacturing a steel pipe stiffening brace member according to claim 7,wherein an end member formed of flat steel with a width larger than alength of a diagonal of the stiffening steel pipe is installed at an endin a longitudinal direction of the main shaft member.
 15. The method ofmanufacturing a steel pipe stiffening brace member according to claim 8,wherein an end member formed of flat steel with a width larger than alength of a diagonal of the stiffening steel pipe is installed at an endin a longitudinal direction of the main shaft member.
 16. The steel pipestiffening brace member according to claim 2, wherein an auxiliary shaftmember formed of flat steel is installed on a side surface of the mainshaft member.
 17. The steel pipe stiffening brace member according toclaim 2, wherein an end member formed of flat steel with a width largerthan a length of a diagonal of the stiffening steel pipe is installed atan end in a longitudinal direction of the main shaft member.
 18. Thesteel pipe stiffening brace member according to claim 3, wherein an endmember formed of flat steel with a width larger than a length of adiagonal of the stiffening steel pipe is installed at an end in alongitudinal direction of the main shaft member.